Upcycling of Waste Polyester Plastic to Carboxylic Acids and Hydrogen by a Ru<sup>δ+</sup>–Ru<sup>0</sup> Dual-Site Catalyst
Yawen Shi, Shengbo Zhang, Xinyong Diao, Zongyang Ya, Hu Ding, Kaihao Cao, Ruhan Wei, Mei Li, Qingling Liu, Na Ji
Abstract
Chemical upcycling of plastic waste into high-value chemicals or fuels could mitigate environmental pollution and create a more sustainable society. Hydrolytic depolymerization is a viable method for polyester recycling but typically requires high temperature to drive this reaction and complete subsequent distillation operations to separate a diol from the aqueous phase. Here, through theoretical screening, we discover a Ru δ+ –Ru 0 dual-site catalyst can achieve the tandem PET (polyethylene terephthalate) depolymerization and in situ reforming of ethylene glycol (EG) under mild conditions. Mechanism studies reveal that the Ru δ+ site can selectively promote adsorption and C–H bond dissociation, yet C–C bond cleavage takes place on both Ru δ+ and Ru 0 sites, which synergistically promotes PET and EG conversion and helps avoid excessive oxidation of intermediates to CO 2 or CO. As a result, this catalyst delivers a conversion of 100% toward PET and EG into high-value organic acids, including terephthalic acid, and high-purity H 2 with a generation rate of 1.03 m 3 kg PET –1 d –1 g Cat –1 at 90 °C. Besides, this catalyst is catalytically active toward a wide scope of substrates, including real-world waste PET products, PET-containing mixed plastics, and other polyester plastics. Techno-economic analysis and environmental assessment show that this integration process can significantly increase net profits and reduce carbon emissions.